Silicide targets for sputtering

ABSTRACT

Metal silicide targets are provided for sputtering which have a density of at least 99%, no more than one coarse silicon phase 10 μm or larger in size that appears, per square millimeter, on the sputter surface, and an oxygen content of at most 150 ppm. They are made by a method which comprises finely grinding a synthesized silicide powder, vacuum annealing the finely ground powder in a hot press die without the application of pressure, and thereafter compacting and sintering the compact to a density of at least 99% by hot pressing. Alternatively, the finely ground powder is vacuum annealed as a presintered body at a density ratio of 50 to 75%, and thereafter is compacted and sintered.

This is a divisional of Ser. No. 08/224,445 filed on Apr. 7, 1994 nowU.S. Pat. No. 5,460,793

BACKGROUND OF THE INVENTION

This invention relates to metal silicide targets for sputtering and amethod of manufacturing the same whereby the formation of particulatematters, or particles, can be substantially decreased from the prior artlevel and an increase in the oxygen content due to fine grinding of thepowder material is avoided. The metal silicide films formed bysputtering process from the metal silicide targets of the invention areuseful for the films of large-scale integrated circuits that involvevery fine wiring and interconnecting line widths and spaces. Theypromise use in present and future semiconductor devices such as highintegration-scale (e.g., 4, 16, and 64-megabit) LSIs and VLSIs.

Polysilicon has hitherto been used in electrodes or wiring orinterconnecting lines of LSI semiconductor devices. The tendency towardgreater complexity of LSI semiconductor devices has caused it to presentthe problem of delay in signal transmission rate due to its resistance.Meanwhile, there is a demand for higher-melting-point materials to beused as electrodes to facilitate the formation of lines byself-alignment technique. Under these circumstances, wiring andelectrodes of metal silicides that possess lower electric resistivitythan polysilicon and are compatible with the silicon gate process havecome into use. Examples of the metal silicides are as follows: tungstensilicides (WSi_(x)), molybdenum silicides (MoSi_(x)), tantalum silicides(TaSi_(x)), titanium silicides (TiSi_(x)), cobalt silicides (CoSi_(x)),chromium silicides (CrSi_(x)), nickel silicides (NiSi_(x)), andsilicides of platinum metals, etc. A film of such a metal silicide isformed by sputtering of a metal silicide target. The metal silicidetarget used often has a silicon/metal molar ratio greatly in excess of2, because a molar ratio x of less than 2 imposes so much stresses onthe resulting film that the film tends to come off.

Metal silicide targets are manufactured by mixing silicon powder andmetal powder in a silicon/metal molar ratio of 2 or more, forming themixture into a synthesized silicide powder, compressing and sinteringthe powder to obtain compacts, and then machining the sintered compactsto a desired shape.

The recent trend toward greater scale of integration of LSIsemiconductor devices (e.g., to 4, 16, and 64-megabits) has reducedtheir wiring line widths to submicron levels. With this tendency,"particles" originating from the target are attracting attention as asubject of growing concern. The term "particles" as used herein meansthe particulate matter that is scattered and flies off from a target onsputtering of the target. The particles deposit directly on the film ona substrate or stick and build up on surrounding walls and parts andthen come off to deposit on the film, inviting severe troubles such asbreaking and shorting of lines. The particle problem is becoming moreand more serious with the progress of integration and refinement of thecircuits of electronic devices. Thus it is noted anew that conventionalsilicide targets are unsuitable for VLSI applications because they emittoo many particles during sputtering.

It has already been recognized in the art that the presence of coarseaggregates of free silicon phases contribute largely to the release ofparticles from metallic silicide targets. On the basis of thisrecognition, e.g., Japanese Patent Application Public Disclosure No.191366/1992 discloses a metal silicide target of a refractory metal andSi characterized in that the average diameter of free Si particles is 30μm or less and the number of free Si particles having diameters of 40 μmor more that appear on the surface and cross section of the target is 50or less per square millimeter, and also a method of manufacturing thetarget. Patent Application Public Disclosure No. 1370/1993 previouslyfiled by the present applicant imposes an additional restriction,introducing a metal silicide target characterized in that the number ofcoarse silicon phases 10 μm or larger in size that are found present inthe sputter surface of the target is 10 or fewer per square millimeter.Also No. 1370/1993 provides after a method of manufacturing suchtargets.

For the manufacture of metal silicide targets with fewer coarse siliconphases, finer raw material silicon and metal powders are used. Herearises another problem; the finer the powders the higher the oxygencontent. Oxygen-rich silicide targets give off oxygen on sputtering,which is detrimental to the properties, such as resistivity, of theresulting film.

OBJECT OF THE INVENTION

The object of the present invention is to establish a technology for themanufacture of metal silicide targets for sputtering that give off aminimum of particles and have low oxygen contents.

SUMMARY OF THE INVENTION

As finer raw material powders are used to reduce particle generation,the amount of the surface oxide formed on the product increases. We havetackled the basically contradictory problems of suppressing particlegeneration and reducing oxygen content. A metal silicide target thatsatisfies both requirements has now been successfully obtained by usinga finely ground metal silicide powder and vacuum annealing the finesilicide powder directly or as a presintered body prior to final hotpressing. On the basis of the above findings, the present inventionprovides:

(1) a metal silicide target for sputtering which has a density of atleast 99%, no more than one coarse silicon phase 10 μm or larger in sizethat appears, per square millimeter, on the sputter surface of thetarget, and an oxygen content of at most 150 ppm,

(2) a method of manufacturing a metal silicide target for sputteringwhich has a density of at least 99%, has no more than one coarse siliconphase 10 μm or larger in size that appears, per square millimeter, onthe sputter surface of the target and has an oxygen content Of at most150 ppm, which comprises preparing a synthesized metal silicide powder,further finely grinding the synthesized metal silicide powder, vacuumannealing the further finely ground metal silicide powder in a hot pressdie without the application of pressure, and thereafter compacting andsintering the annealed powder to a density of at least 99% by a hotpress, and

(3) a method of manufacturing a metal silicide target for sputteringwhich has a density of at least 99%, has no more than one coarse siliconphase 10 μm or larger in size that appears, per square millimeter, onthe sputter surface of the target and has an oxygen content of at most150 ppm, which comprises preparing a synthesized metal silicide powder,further finely grinding the synthesized metal silicide powder, preparinga presintered body at a density ratio of 50 to 75% of the further groundmetal silicide powder, vacuum annealing the presintered body, andthereafter compacting and sintering the annealed presintered body to adensity of at least 99% by a hot press.

The above mentioned method may further include controlling the arearatio of silicon phases that appear on the sputter surface to 23% orless, and at least partly removing the deformed layer on the targetsurface to attain a surface roughness ranging from more than 0.05 μm to1 μm.

There has been no literature as to any attempt at concurrently solvingthe particle problem and the oxygen content problem. Patent ApplicationPublic Disclosure No. 70270/1987 introduces a process of hot pressing asilicide powder to manufacture a high-density silicide target. It doesnot refer to the amount of coarse silicon phases that appear on thesputter surface, in recognition of the particle problem. PatentApplication Public Disclosure Nos. 58866/1986, 136964/1986, and58865/1986 teach the manufacture of silicide targets with an oxygencontent of 7 to 19 ppm by either heating a presintered mass of silicidewith a density of 48 to 95% above the melting temperature of Si orimpregnating the mass with molten Si. These references are all silent onthe particle problem. In the present invention, avoiding the emergenceof a molten phase is essential for the prevention for particlegeneration as well as of Si phase growth.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the invention, a fine enough metal silicide powder isused for the manufacture of a metal silicide target so as to limit thenumber of coarse silicon phases 10 μm or larger in size that appears onthe target sputter surface to no more than one particle per squaremillimeter to and attain a target density of at least 99% so as toreduce the voids. Moreover, prior to the final step of hot pressing, thefine metal silicide powder is vacuum annealed directly or as apresintered body. In this way both the decrease in the number ofparticles formed and the reduction of the oxygen content aresimultaneously accomplished.

In addition, desirably, the area ratio of silicon phases that appear onthe sputter surface is restricted to 23% or less, whereby overallcontrol of the probability of free silicon generation is effected. Thedeformed layer on the target surface is partly removed to attain asurface roughness ranging from more than 0.05 μm to 1 μm. Theserestrictions substantially reduce the amount of the early-stageparticles that come out mostly at the early stage of sputtering, therebysharply decreasing the amount of particle generation. Thus the reductionof both early-stage particle generation and particle generation at thestabilized stage is realized. If there are particles resulting fromearly-stage particle generation, they deposit largely on the targetsurface with the possibility of coming off during the stable period. Thereduction of early-stage particle generation lessens the possibility ofsecondary particle generation.

The raw material metal silicide powder is prepared, e.g., by the methoddisclosed in Patent Application Public Disclosure No. 70270/1987 whichconsists of mixing metal and silicon powders, synthesizing, grinding,and sieving. It is advisable to make the particle size of thesynthesized metal silicide powder uniform by dry sieving it beforehand,preferably to 50 mesh or finer, more preferably to 200 mesh or finer.

Desirably, the metal and silicon raw material powders are mixed by aV-type mixer or the like in as low a Si/metal molar ratio as possiblelower than commonly used ratios, so that the area ratio of siliconphases that ultimately appear on the sputter surface of the target is23% or less, within the limits of performance allowance of the metalsilicide thin film that is eventually formed. For example, the followingmolar ratios are recommended:

    ______________________________________                                        Si/W molar ratio = 2.25                                                                         Si/Mo molar ratio = 2.15                                    Si/Ti molar ratio = 2.23                                                                        Si/Ta molar ratio = 2.20                                    Si/Cr molar ratio = 2.20                                                                        Si/Co molar ratio = 2.20                                    Si/Ni molar ratio = 2.20                                                                        Si/Pt molar ratio = 1.20                                    ______________________________________                                    

It is usual to set the amount of silicon in a slight excess forcompensating the volatilization loss in the subsequent synthesis step.The amount silicon lost by volatilization can be precisely grasped fromthe equipment and conditions to be used for the operation. Desirably, aminimum excess amount of silicon should be used. The powder mixture issubjected to synthesis treatment in a high-temperature vacuum furnace.The synthesis reaction is exothermic. The conditions for silicidesynthesis are as follows:

    ______________________________________                                        Degree of vacuum:                                                                         10.sup.-3 ˜ 10.sup.-5 Torr                                  Temperature:                                                                              800 ˜ 1300° C. (varies with metals)                  Time:       sufficient time for the synthesis                                             reaction M + xSi→MSi.sub.x (x = 2.00 ˜ 2.33,                     but for platinum group metals                                                 x = 1.00 ˜ 1.26)                                            ______________________________________                                    

The silicide thus synthesized is cooled under vacuum, cooled down to 50°C. or below, and taken out of the furnace and ground. Care must be takento avoid an increase in the O₂ content during grinding by a ball mill orthe like, e.g., by performing the grinding in an Ar-replaced atmosphere.To prevent the contamination with Fe or other impurities, it isdesirable that the balling mill use balls coated with or made of thesame metal as that which is handled.

As for the raw material metal powder for the preparation of a metalsilicide, a metal powder pulverized or finely crushed by a grindingequipment, e.g., a ball mill is used. The maximum particle diameter ofthe metal powder to be used, in terms of the aggregated secondaryparticles, is, e.g., 60 μm or less, preferably 20 μm or less. Examplesof useful metals are tungsten, molybdenum, titanium, tantalum, chromium,cobalt, nickel, and platinum group metals.

The raw material silicon powder is prepared by grinding a startingmaterial, such as polysilicon chips for semiconductor use, e.g., in aball mill in an argon atmosphere for 12 to 28 hours.

The metal and silicon powders to be used desirably as starting materialscontain radioactive elements, alkali metals, transition metals, heavymetals, oxygen, or/and other substances, all reduced in amounts tominimal traces. Raw material silicon powders ranging in purity from 5 to9N (99.999˜99.9999999 wt %) or even higher are readily available on themarket. With raw material metal powders too, the present applicant hasalready established a technology of reducing the contents, such as ofradioactive elements, alkali metals, transition elements, and heavymetals, in tungsten, molybdenum, cobalt, tantalum, and many other metalsto just traces by a combination of chemical refining (recrystallization)and physical refining (arc melting).

Where an adjustment of the molar ratio is required, a metal silicidepowder which is free from coarse silicon particles and has a molar ratiodifferent from that of the original metal silicide being produced isadded according to the need. The metal silicide powder to be added isfine enough to pass through a 50-mesh sieve, preferably a 200-meshsieve. The original silicide powder and the additional silicide powderare thoroughly mixed using, e.g., a V-type mixer. The adjustment ofcomposition with the use of a silicide powder, rather than siliconpowder, before hot pressing, helps prevent particle generation owing tosilicon aggregation. The free silicon particles entrapped in the siliconaggregate are partly responsible for the particle generation. Thus theaddition of silicide powder rather than silicon powder which is easilyaggregatable for the compositional adjustment prior to hot pressinginhibits the generation of particles.

Under the invention the metal silicide powder is secondarily pulverizedby a fine grinding mill and coarse particles 20 μm or larger in size areeliminated. Fine grinding mills available commercially may be used whichprotect the metal silicide powder charge from contamination. Examples ofproprietary equipment are as follows:

(a) "Superfine Grinding Å ng-Mill" (manufactured by Hosokawa Micron Co.,Ltd.)

(b) "Supersonic Jet Grinder Models I and PJM" (by Nippon PneumaticIndustry Co., Ltd.)

(c) "Current Jet" (by Nisshin Engineering Co., Ltd.)

(d) "Single Track Jet Mill" (by Seishin Kigyo Co., Ltd.)

(e) "New Superfine Grinding Mill" (by Kawasaki Heavy Industries Ltd.)

(f) "Counter-Jet Mill" (by Itomah Engineering Co., Ltd.)

(g) "CF Mill" (by Ube Industries, Ltd.)

By the secondary pulverization, the percentage of coarse particles 10 μmor larger in size, especially particles larger than 8 μm, can be reducedto almost zero.

The fine metal silicide powder so obtained has an oxygen content of morethan 1000 ppm, usually between 1000 and 2000 ppm. Using this fine metalsilicide powder and by adopting (1) direct hot pressing or (2) indirecthot pressing, deoxygenation and densification are effected formanufacture of a metal silicide composition having at least one targetsurface suitable for sputtering.

In direct hot pressing, the fine metal silicide powder is directlyfilled in a hot press die. Ordinarily, hot pressing is conducted whileadequately compacting the powder from a temperature elevation procedure,but under the invention, by contrast, the powder is not compacted at allwhile the temperature is raised in a state where adequate evacuation isfeasible. After the arrival at a predetermined temperature, compactiondoes not immediately follow. The evacuation and heating are maintainedfor an additional period of 1 to 10 hours, and then ordinary hotpressing is initiated. In conventional hot pressing practice, the powderis compacted before the temperature is allowed to rise, anunsatisfactory deoxygenation effect is achieved. In the case of amolybdenum silicide, for example, a silicide powder containing 1200 ppmof oxygen will yield a target with an oxygen content decreased at mostto 1000 ppm. When the molybdenum silicide is heated without priorcompaction but in a state capable of being thoroughly evacuated, and isheld in the heated condition, the original oxygen content of 1200 ppmdrops to only 60 to 100 ppm in 4 hours and down even to 40 ppm in 10hours. With a tungsten silicide, for example, the oxygen content islowered from 1400 ppm in the material silicide to only 30 ppm in theproduct obtained after 10 hours of holding.

The holding time varies with the quantity of silicide to be hot pressed,but it usually begins to produce a deoxygenation effect in an hour, and10 hours of holding is enough to meet the current deoxygenationrequirement. Longer holding for more than 10 hours is rather deleteriousbecause of productivity drop, contamination with carbon from the die,and other adverse effects upon the holding. The mechanism ofdeoxygenation is presumably explained by the reaction Si+O→SiO(g) orSiO₂ +Si→2SiO (g). Hot pressing causes a slight change in the Sicontent, and it decreases the original Si/metal molar ratio by 0.02 to0.05.

In indirect hot pressing, a fine silicide powder is first formed into abriquet with a density of 50 to 75%. For the briquetting, a method usinga cold press, cold isostatic pressing (CIP), low-temperature,low-pressure hot press or the like is employed. The briquet is heated to1000° to 1380° C. while being evacuated to a high degree of vacuum andis held in that state for 1 to 10 hours. Once cooled, the briquet ispacked in a hot press die and hot pressed in the usual manner to yield asilicide target. In the briquet the oxygen content is on the same levelas in the silicide powder. The briquet density is specified to rangefrom 50 to 75% for the following reasons. A density below 50% makes thebriquet difficult to handle, although it favors deoxygenation. Thebriquet must be strong to some degree, just enough for handling. Adensity above 75% eliminates thoroughly opened pores, making evacuationthroughout difficult or impossible, which in turn leads to inadequatedeoxygenation. If the heating temperature is below 1000° C., thedeoxygenation effect is limited, while a temperature above 1380° C. iseffective for oxygen removal but is prone to induce the grain growth ofthe Si phase. It is imperative to prevent the emergence of a liquid Siphase for the preclusion of unwanted particle generation. The holdingtime ranges from 1 to 10 hours depending on the temperature used,because a holding time that is too short results in insufficientdeoxygenation, and prolonged holding reduces the productivity. For theother aspects of the indirect hot pressing operation, reference is madeto the above description of direct hot pressing.

Ordinary hot pressing is then carried out. It is important that thisstep be so implemented as to compact the silicide powder to anadequately high density in a density ratio of at least 99%, preferablyat least 99.99%. Application of a preload to the compact at the time ofhot pressing, and holding the state for some time after the pressing, isa recommended practice. The conditions for hot pressing are as follows:

    ______________________________________                                        Degree of vacuum:                                                                          10.sup.-5 ˜ 10.sup.-6 Torr                                 Temperature: 900 ˜ 1380° C. (depending on the metal)             Press pressure:                                                                            250 ˜ 600 kg/cm.sup.2                                      Time:        30 min. ˜ 3 hr.                                            Holding time:                                                                              the longer the better, the minimum                                            period being 30 min.                                             ______________________________________                                    

For the hot pressing the metal silicide powder is placed into acompaction mold and the temperature increased. When a target temperaturebetween 900° C. and 1380° C. has been reached, the application of apredetermined press pressure is initiated while the above temperaturelevel is being maintained. The application of the pressure graduallyreduces the thickness of the green compact. Past a given time point thecompact thickness becomes constant and no more reduction of thicknesstakes place. In this state the application of the press pressure usuallyis discontinued. To achieve higher density it is effective to apply apreload to the compact at the time of pressing and hold it for sometime, say 30 minutes or more, after the above time point. For thepurposes of the invention this procedure is called "holding". In thisway a high-density sintered body having a density of 99% or more isobtained.

Pressing a compact of fine synthesized metal silicide powder at elevatedtemperature for a sufficient period of time allows intergranularsintering to proceed until a uniform sintered structure results. The hotpressing in this case must be solid-phase sintering. Many methods of theprior art produce a liquid phase during the time period of sintering,which has been known to be prone to particle generation. It is for thisreason that the present invention adopts solid-phase sintering under thespecified conditions.

After the pressing, the pressed product is taken out from the die and isfinished by machining it to a sputtering target with specified shape anddimension. Finally the target produced is subjected to a deformedlayer-removal step that is preferably incorporated under the presentinvention whereby the deformed layer is partly removed from the targetand the surface is smoothened. The process of deformed layer removal isperformed by ion milling, sputtering, electropolishing, chemicaletching, lapping, polishing, or other suitable technique for surfacetreatment. These techniques are all effective as deformed layer-removalsteps by which a target surface layer from 20 to 100 μm thick is removedstrain-free. Such a surface treatment decreases the surface roughness(R_(a)) from the pretreatment value of about 5.0 μm to 1.0 μm or less.The step is followed by ultrasonic cleaning with isopropyl alcohol orthe like and vacuum drying to provide a product completely freed fromthe contaminants that had deposited on the surface during the surfacetreatment. Lastly, the target thus obtained is bonded to a backingplate.

The deformed layer-removal step, along with the limitation of the arearatio of silicon phases appearing on the sputter surface to 23% or less,has been found very effective for controlling the early-stage particlegeneration. In the case of a metal silicide target, a considerableamount of particles are generated at the early stage of sputtering andthe particles deposit, e.g., on the inner walls of equipment, build up,and come off onto the film. Controlling the early-stage particlegeneration, therefore, reduces substantially the total number ofparticles that deposit on a wafer.

Thus a metal silicide target having a density of at least 99% isobtained which contains no more than one coarse silicon phase 10 μm orlarger in size that appears on the sputter surface per squaremillimeter. The oxygen content of the target is no more than 150 ppm.

Desirably, as stated above, the area ratio of silicon phases that appearon the sputter surface is restricted to 23% or less, and the deformedlayer on the surface is removed to attain a surface roughness of frommore than 0.05 μm to 1 μm. Thus, the use of a finely ground metalsilicide powder reduces the number of coarse silicon phase that appearson the sputter surface to one or fewer per square millimeter and attainsa target density of 99% or more to decrease the voids. The overallcontrol of the probability of free silicon generation is effectedthrough the restriction of the area ratio of the silicon phases thatappear on the sputter surface. These restrictions are combined with theremoval of the deformed layer from the surface and restricting thesurface roughness to the range from more than 0.05 μm to 1 μm to reducethe amount of particle generation substantially from the ordinary level.

The area ratio of silicon phases that appear on the sputter surface andthe number of coarse silicon phases 10 μm or larger in diameter thatoccur were measured and counted visually under a microscope with amagnification of 100×.

EXAMPLES

The invention is illustrated by the following examples and comparativeexamples.

Example 1

A molybdenum silicide powder (Si/Mo molar ratio=2.30), prepared by finegrinding on a counter jet mill to the maximum particle diameter of 10 μmand an oxygen concentration of 1200 ppm, was charged into a hot pressdie and kept there under vacuum at 1300° C. for 4 hours. The charge wasthen hot pressed at 1300° C. A molybdenum silicide target having adensity ratio of more than 99.99% and an oxygen concentration of 50 ppmwas obtained. Its Si/Mo molar ratio decreased by 0.02. The largest Siphase that appeared on the sputter surface measured 10 μm in diameterand numbered only one per square millimeter. A molybdenum silicide filmwas formed by sputtering from this target, and the particles on a waferwere determined by the laser method. Particles 0.3 μm or larger in sizefound on a 6-in wafer numbered 10.

Example 2

The same molybdenum silicide powder as used in Example 1 was formed bycold pressing into a briquet with a density ratio of 60%. The briquetwas heated under vacuum at 1300° C. for 4 hours. The briquet now had adensity of 88% an oxygen concentration of 130 ppm. It was then hotpressed to obtain a target with a density of more than 99.99% and anoxygen concentration of 130 ppm. The Si/Mo molar ratio decreased by0.02. The largest Si Phase that appeared on the sputter surface measured10 μm in diameter and numbered again only one per square millimeter. Amolybdenum silicide film was formed by sputtering from this target, andthe particles on a wafer were determined by the laser method. Particles0.3 μm or larger in size found on a 6-in. wafer numbered 10.

Example 3

A tungsten silicide powder, prepared by fine grinding on a counter jetmill to the maximum particle diameter of 8 μm and an oxygenconcentration of 1500 ppm, was held in a die under vacuum at 1300° C.for 10 hours, and then hot pressed at 1300° C. A tungsten silicidetarget having a density ratio of more than 99.99% and an oxygenconcentration of 30 ppm was obtained. Its Si/W molar ratio decreased by0.03. The largest Si phase that appeared on the sputter surface measured8 μm in diameter and there was no Si phase 10 μm or larger. A tungstensilicide film was formed by sputtering from this target, and theparticles on a wafer were determined by the laser method. Particles 0.3μm or larger in size found on a 6-in. wafer numbered 8.

Comparative Example 1

The molybdenum silicide powder of Examples 1 and 2 was used and hotpressed in the usual manner, with a load applied from the beginning. Atarget having a density ratio of more than 99.99% and an oxygenconcentration of 1000 ppm was obtained. There occurred no decrease inthe molar ratio. The number of the Si phase 10 μm or larger in size thatappeared on the sputter surface was one per square millimeter.

ADVANTAGES OF THE INVENTION

The problems of particle generation and contamination with oxygenassociated with the use of metal silicide targets have been tackled andsolved successfully for the first time in the art. A metal silicidetarget for sputtering having a density of at least 99% having, no morethan one coarse silicon phase 10 μm or larger in size that appears, persquare millimeter, on the sputter surface, and having an oxygen contentof at most 150 ppm can now be manufactured by controlling the amount ofcoarse silicon phases 10 μm or larger in size that appear on the sputtersurface and by improving the sintering process. In addition, the amountof free particle generation can further be reduced by slightlydecreasing the silicon/metal molar ratio, lowering the area ratio ofsilicon phases that appear on the sputter surface, and partiallyremoving the deformed layer from the surface. The invention thuscontributes to the practical application of metal silicides that havemuch promising future as films for more complex LSIs with lowerresistivities and narrower line widths and spaces than before, to thesemiconductor devices of tomorrow, e.g., higher integration-scale (4,16, and 64-megabit) LSIs and VLSIs.

What is claimed is:
 1. A metal silicide target for sputtering which hasa density of at least 99%, no more than one coarse silicon phase 10 μmor larger in size that appears, per square millimeter, on the sputtersurface of the target, an area ratio of silicon phases that appear onthe sputter surface of 23% or less, a surface roughness ranging frommore than 0.05 μm to 1 μm attained by at least partly removing adeformed layer on the target surface, and an oxygen content of at most150 ppm.
 2. A metal silicide target for sputtering which has a densityof at least 99%, has no more than one coarse silicon phase 10 μm orlarger in size that appears, per square millimeter, on the sputtersurface of the target, has an area ratio of silicon phases that appearon the sputter surface of 23% or less, has a surface roughness rangingfrom more than 0.05 μm to 1 μm, and has an oxygen content of at most 150ppm, manufactured by a process which comprises:preparing a synthesizedmetal silicide powder, wherein the synthesized metal silicide powder hascoarse particles 20 μm or larger in size, further finely grinding thesynthesized metal silicide powder so that coarse particles 20 μm orlarger in size are eliminated, vacuum annealing the further finelyground metal silicide powder in a hot press die without the applicationof pressure to remove at least a part of the oxygen in the form of SiO₂,compacting and sintering the annealed metal silicide powder to a densityof at least 99% by a hot press, and at least partly removing a deformedlayer on the target surface to attain a surface roughness ranging frommore than 0.05 μm to 1 μm.
 3. A metal silicide target for sputteringwhich has a density of at least 99%, has no more than one coarse siliconphase 10 μm or larger in size that appears, per square millimeter, onthe sputter surface of the target, has an area ratio of silicon phasesthat appear on the sputter surface of 23% or less, has a surfaceroughness ranging from more than 0.05 μm to 1 μm, and has an oxygencontent of at most 150 ppm, manufactured by a process whichcomprises:preparing a synthesized metal silicide powder, wherein thesynthesized metal silicide powder has coarse particles 20 μm or largerin size, further finely grinding the synthesized metal silicide powderso that coarse particles 20 μm or larger in size are eliminated,preparing a presintered body at a density ratio of 50 to 75% of thefurther ground metal silicide powder, vacuum annealing the furtherpresintered body to remove at least a part of the oxygen in the form ofSiO₂, compacting and sintering the annealed presintered body to adensity of at least 99% by a hot press, and at least partly removing adeformed layer on the target surface to attain a surface roughnessranging from more than 0.05 μm to 1 μm.